To be fair, there are a lot of blood-XYZ barriers: https://en.m.wikipedia.org/wiki/Blood%E2%80%93brain_barrier#See_also https://en.m.wikipedia.org/wiki/Blood%E

To be fair, there are a lot of blood-XYZ barriers: https://en.m.wikipedia.org/wiki/Blood%E2%80%93brain_barrier#See_also https://en.m.wikipedia.org/wiki/Blood%E2%80%93brain_barrier#...